The primary goal of this study is to determine the feasibility and safety of giving two doses of denileukin diftitox (DD) at days 0 and 21 post autologous stem cell transplantation in a dose escalation fashion. Secondary goals include evaluating the the effect of DD on the number and percentage of T-regs in the peripheral blood post transplant at each dose level, the effect of DD on T cell (CD4/CD8) reconstitution post transplant at each dose level and determining the time to engraftment: absolute neutrophil count (>0.5 x 10^9/L for 3 consecutive days), and platelet (>20X 10^9/L for 3 consecutive days).